Recently, the development of the backbone network communication line as mainly focusing on the optical fiber communication technology is proceeding steadily and, in such a situation, the electronic wirings in the information terminal are becoming a bottleneck. Against such background, instead of the conventional electric circuit substrate in which all signal transmissions are made by using the electric signal, the optoelectronic composite substrate (optical waveguide device) of the type that transmits high-speed parts by the light has been proposed, in order to compensate the limit of transmission speed of the electric signal.
In the optoelectronic composite substrate, the light signal is transmitted by the optical waveguide including such a structure in which the core layer is surrounded by the cladding layers.
In an example of the optical waveguide manufacturing method, first the lower cladding layer, the core layers, and the upper cladding layer are formed sequentially on the substrate. Then, the resultant structure is processed so as to divide the core layer from the upper cladding layer side, and thus the groove portion having the inclined surface is formed. Then, the metal layer is partially formed on the groove portion by the mask vapor deposition, or the like, and thus the light path conversion mirror is obtained.
Then, a light which propagates through the core layer is made to reflect in the vertical direction by the metal layer (light path conversion mirror) on the inclined surface of the groove portion, thus the light path is converted.
A related art is disclosed in Japanese Laid-open Patent Publication No. 2005-70141 and Japanese Patent No. 4234061.
In the prior art, after the groove portion having the inclined surface is formed by processing the optical waveguide, the metal layer is partially formed on the groove portion only. Therefore, there exists such problems that it takes much time when forming the light path converting portion and thus a manufacturing efficiency is bad, and that an increase in cost is also brought about because the particular film forming equipment such as the mask vapor deposition, or the like is needed.